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MoorProps streamlining and removing specific gravity:
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- Removing specific gravity as a MoorProps input option since
  the reference density can be unclear and a source of discrepancy.
  Just using dvol_dnom and material density now.
- Trimming mass inputs to be mass/d^2 only, to avoid potential
  issues with buoyancy/density assumptions. It's all we use anyway.
- Updated MoorProps default YAML with the above edits.
- Updated MoorProps helper functions with the above changes, and also
  trimmed error checking to only be in the load function, since after
  that point the data should already be verified and may be used many
  times in the loop so we want to prioritize speed.
- Some function comment updates.
  • Loading branch information
@mattEhall
mattEhall committed Oct 31, 2023
1 parent 367a66b commit 2cdf4e0
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8 changes: 0 additions & 8 deletions moorpy/MoorProps_default.yaml
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Original file line number Diff line number Diff line change
Expand Up @@ -3,10 +3,7 @@
# lineProps -> [line material name] -> [line material coefficients]

# All possible lineProps coefficients are as follow:
# mass_0 : # linear mass density offset [kg/m]
# mass_d : # linear mass density per diameter [kg/m^2]
# mass_d2 : # linear mass density per diameter^2 [kg/m^3]
# mass_d3 : # linear mass density per diameter^3 [kg/m^4]
#
# MBL_0 : # minimum breaking load offset [N]
# MBL_d : # minimum breaking load per diameter [N/m]
Expand All @@ -23,7 +20,6 @@
#
# dvol_dnom : # volume-equivalent diameter per nominal diameter [-]
# density : # density of the line material [kg/m^3] (e.g., chain density = 7850 kg/m^3)
# spec_grav : # specific gravity of the line material [-] (relative to a reference density, usually water)
# NOTE: Only one of the above three variables can be used as input!
#
# cost_0 : # cost offset [$/m]
Expand All @@ -46,10 +42,6 @@

lineProps:

water_reference:
density : 1025.0 # [kg/m^3]


chain : # R4 grade studless chain (the default chain that will be used when linetypename='chain')
mass_d2 : 20.01e3 # linear mass density per diameter^2 [kg/m/m^2]
EA_d3 : -3.927e7 # stiffness per diameter^3 [N/m^3]
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148 changes: 58 additions & 90 deletions moorpy/helpers.py
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Original file line number Diff line number Diff line change
Expand Up @@ -629,39 +629,30 @@ def dsolvePlot(info):

def getLineProps(dnommm, material, lineProps=None, source=None, name="", rho=1025.0, g=9.81, **kwargs):
'''Sets up a dictionary that represents a mooring line type based on the
specified diameter and material type. The
- This function requires at least one input: the line diameter in millimeters.
- The rest of the inputs are optional: describe the desired type of line (chain, polyester, wire, etc.),
the type of chain (studless or studlink), the source of data (Orcaflex-original or altered), or a name identifier
- The function will output a MoorPy linetype object
# support options for :
# 1. dictionary passed in (this is what will be done when called from a System method)
(a) by default, System will load in MoorPy's default line property information YAML
(b) or user specify's alternate YAML file when making the system
# 2. yaml filename pass in or use default moorpy yaml and load yaml (used when called independently)
System.linePropsDatabase will be a dictionary of stored YAML coefficients
System.lineTypes will become a dictionary of LineType DICTIONARIES
specified diameter and material type. The returned dictionary can serve as
a MoorPy line type. Data used for determining these properties is a MoorPy
lineTypes dictionary data structure, created by loadLineProps. This data
can be passed in via the lineProps parameter, or a new data set can be
generated based on a YAML filename or dictionary passed in via the source
parameter. The lineProps dictionary should be error-checked at creation,
so it is not error check in this function for efficiency.
Parameters
----------
dnommm : float
nominal diameter [mm].
material : string
string identifier of the material type be used.
lineProps : dictionary
A MoorPy lineProps dictionary data structure containing the property scaling coefficients.
source : dict or filename (optional)
YAML file name or dictionary containing line property scaling coefficients
name : any dict index (optional)
Identifier for the line type (otherwise will be generated automatically).
Identifier for the line type (otherwise will be generated automatically).
rho : float (optional)
Water density used for computing apparent (wet) weight [kg/m^3].
g : float (optional)
Gravitational constant used for computing weight [m/s^2].
'''

if lineProps==None and source==None:
Expand All @@ -680,30 +671,19 @@ def getLineProps(dnommm, material, lineProps=None, source=None, name="", rho=102
# calculate the relevant properties for this specific line type
mat = lineProps[material] # shorthand for the sub-dictionary of properties for the material in question
d = dnommm*0.001 # convert nominal diameter from mm to m
mass = mat['mass_0'] + mat['mass_d']*d + mat['mass_d2']*d**2 + mat['mass_d3']*d**3
mass = mat['mass_d2']*d**2
MBL = mat[ 'MBL_0'] + mat[ 'MBL_d']*d + mat[ 'MBL_d2']*d**2 + mat[ 'MBL_d3']*d**3
EA = mat[ 'EA_0'] + mat[ 'EA_d']*d + mat[ 'EA_d2']*d**2 + mat[ 'EA_d3']*d**3 + mat['EA_MBL']*MBL
cost =(mat['cost_0'] + mat['cost_d']*d + mat['cost_d2']*d**2 + mat['cost_d3']*d**3
+ mat['cost_mass']*mass + mat['cost_EA']*EA + mat['cost_MBL']*MBL)

# internally calculate the volumetric diameter using one of three options
if mat['dvol_dnom'] is not None and mat['material_density'] is None and mat['spec_grav'] is None: # if only 'dvol_dnom' is specified in the source
d_vol = mat['dvol_dnom']*d # [m]
elif mat['material_density'] is not None and mat['dvol_dnom'] is None and mat['spec_grav'] is None: # if only 'density' is specified in the source
material_density = mat['density'] # [kg/m^3]
d_vol = np.sqrt((mass/material_density)*(4/np.pi)) # [m]
elif mat['spec_grav'] is not None and mat['dvol_dnom'] is None and mat['material_density'] is None: # if only 'spec_grav' is specified in the source
water_density = lineProps['water_reference']['density'] # [kg/m^3]
material_density = (mat['spec_grav']/(water_density/1000))*1000 # [kg/m^3]
d_vol = np.sqrt((mass/material_density)*(4/np.pi)) # [m]
else:
raise ValueError("Only one parameter can be specified to calculate the volumetric diameter. Choose either 'dvol_dnom', 'density', or 'spec_grav'")

# use the volumetric diameter to calculate the weight per unit length (could have also used mass, water density, and material density)
# internally calculate the volumetric diameter using a ratio
d_vol = mat['dvol_dnom']*d # [m]

# use the volumetric diameter to calculate the apparent weight per unit length
w = (mass - np.pi/4*d_vol**2 *rho)*g

# stiffness values for viscoelastic approach
#EAs = mat['EA_MBL']*MBL # quasi-static stiffness: Krs x MBL [N]
EAd = mat['EAd_MBL']*MBL # dynamic stiffness constant: Krd alpha term x MBL [N]
EAd_Lm = mat['EAd_MBL_Lm'] # dynamic stiffness Lm slope: Krd beta term (to be multiplied by mean load) [-]

Expand Down Expand Up @@ -733,10 +713,14 @@ def loadLineProps(source):
Parameters
----------
source : dict or filename
YAML file name or dictionary containing line property scaling coefficients
Returns
-------
dictionary
LineProps dictionary listing each supported mooring line type and
subdictionaries of scaling coefficients for each.
'''

if type(source) is dict:
Expand Down Expand Up @@ -764,57 +748,41 @@ def loadLineProps(source):
output = dict() # output dictionary combining default values with loaded coefficients

# combine loaded coefficients and default values into dictionary that will be saved for each material
for mat, props in lineProps.items():
if mat != 'water_reference':
output[mat] = {}
output[mat]['mass_0' ] = getFromDict(props, 'mass_0' , default=0.0)
output[mat]['mass_d' ] = getFromDict(props, 'mass_d' , default=0.0)
output[mat]['mass_d2' ] = getFromDict(props, 'mass_d2' , default=0.0)
output[mat]['mass_d3' ] = getFromDict(props, 'mass_d3' , default=0.0)
output[mat]['EA_0' ] = getFromDict(props, 'EA_0' , default=0.0)
output[mat]['EA_d' ] = getFromDict(props, 'EA_d' , default=0.0)
output[mat]['EA_d2' ] = getFromDict(props, 'EA_d2' , default=0.0)
output[mat]['EA_d3' ] = getFromDict(props, 'EA_d3' , default=0.0)
output[mat]['EA_MBL' ] = getFromDict(props, 'EA_MBL' , default=0.0)
output[mat]['EAd_MBL' ] = getFromDict(props, 'EAd_MBL' , default=0.0)
output[mat]['EAd_MBL_Lm']= getFromDict(props, 'EAd_MBL_Lm',default=0.0)

output[mat]['MBL_0' ] = getFromDict(props, 'MBL_0' , default=0.0)
output[mat]['MBL_d' ] = getFromDict(props, 'MBL_d' , default=0.0)
output[mat]['MBL_d2' ] = getFromDict(props, 'MBL_d2' , default=0.0)
output[mat]['MBL_d3' ] = getFromDict(props, 'MBL_d3' , default=0.0)
#output[mat]['dvol_dnom'] = getFromDict(props, 'dvol_dnom', default=1.0)

if 'dvol_dnom' in props and 'density' not in props and 'spec_grav' not in props:
output[mat]['dvol_dnom'] = getFromDict(props, 'dvol_dnom')
output[mat]['material_density'] = None
output[mat]['spec_grav'] = None
elif 'density' in props and 'dvol_dnom' not in props and 'spec_grav' not in props:
output[mat]['dvol_dnom'] = None
output[mat]['material_density'] = getFromDict(props, 'density')
output[mat]['spec_grav'] = None
elif 'spec_grav' in props and 'dvol_dnom' not in props and 'density' not in props:
output[mat]['dvol_dnom'] = None
output[mat]['material_density'] = None
output[mat]['spec_grav'] = getFromDict(props, 'spec_grav')
else:
raise ValueError("Only one parameter can be specified to calculate the volumetric diameter. Choose either 'dvol_dnom', 'density', or 'spec_grav'")

output[mat]['cost_0' ] = getFromDict(props, 'cost_0' , default=0.0)
output[mat]['cost_d' ] = getFromDict(props, 'cost_d' , default=0.0)
output[mat]['cost_d2' ] = getFromDict(props, 'cost_d2' , default=0.0)
output[mat]['cost_d3' ] = getFromDict(props, 'cost_d3' , default=0.0)
output[mat]['cost_mass'] = getFromDict(props, 'cost_mass', default=0.0)
output[mat]['cost_EA' ] = getFromDict(props, 'cost_EA' , default=0.0)
output[mat]['cost_MBL' ] = getFromDict(props, 'cost_MBL' , default=0.0)
for mat, props in lineProps.items():
output[mat] = {}
output[mat]['mass_d2' ] = getFromDict(props, 'mass_d2') # mass must scale with d^2
output[mat]['EA_0' ] = getFromDict(props, 'EA_0' , default=0.0)
output[mat]['EA_d' ] = getFromDict(props, 'EA_d' , default=0.0)
output[mat]['EA_d2' ] = getFromDict(props, 'EA_d2' , default=0.0)
output[mat]['EA_d3' ] = getFromDict(props, 'EA_d3' , default=0.0)
output[mat]['EA_MBL' ] = getFromDict(props, 'EA_MBL' , default=0.0)
output[mat]['EAd_MBL' ] = getFromDict(props, 'EAd_MBL' , default=0.0)
output[mat]['EAd_MBL_Lm']= getFromDict(props, 'EAd_MBL_Lm',default=0.0)

elif mat == 'water_reference':
output[mat] = {}
output[mat]['density'] = getFromDict(props, 'density', default=1025.0)
output[mat]['MBL_0' ] = getFromDict(props, 'MBL_0' , default=0.0)
output[mat]['MBL_d' ] = getFromDict(props, 'MBL_d' , default=0.0)
output[mat]['MBL_d2' ] = getFromDict(props, 'MBL_d2' , default=0.0)
output[mat]['MBL_d3' ] = getFromDict(props, 'MBL_d3' , default=0.0)
output[mat]['dvol_dnom'] = getFromDict(props, 'dvol_dnom', default=1.0)

# special handling if material density is provided
if 'density' in props:
if 'dvol_dnom' in props:
raise ValueError("Only one parameter can be specified to calculate the volumetric diameter. Choose either 'dvol_dnom' or 'density'.")
else:
mass_d2 = output[mat]['mass_d2']
material_density = getFromDict(props, 'density')
output[mat]['dvol_dnom'] = np.sqrt((mass_d2/material_density)*(4/np.pi))

else:
raise ValueError(f"Mooring property dictionary entry '{mat}' not supported at this time")

# cost coefficients
output[mat]['cost_0' ] = getFromDict(props, 'cost_0' , default=0.0)
output[mat]['cost_d' ] = getFromDict(props, 'cost_d' , default=0.0)
output[mat]['cost_d2' ] = getFromDict(props, 'cost_d2' , default=0.0)
output[mat]['cost_d3' ] = getFromDict(props, 'cost_d3' , default=0.0)
output[mat]['cost_mass'] = getFromDict(props, 'cost_mass', default=0.0)
output[mat]['cost_EA' ] = getFromDict(props, 'cost_EA' , default=0.0)
output[mat]['cost_MBL' ] = getFromDict(props, 'cost_MBL' , default=0.0)

return output


Expand Down
4 changes: 2 additions & 2 deletions moorpy/system.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3182,9 +3182,9 @@ def plot(self, ax=None, bounds='default', rbound=0, color=None, **kwargs):
else:
j = j + 1
if color==None and 'material' in line.type:
if 'chain' in line.type['material'] or 'Cadena80' in line.type['material']:
if 'chain' in line.type['material']:
line.drawLine(time, ax, color=[.1, 0, 0], endpoints=endpoints, shadow=shadow, colortension=colortension, cmap_tension=cmap_tension)
elif 'rope' in line.type['material'] or 'polyester' in line.type['material'] or 'Dpoli169' in line.type['material']:
elif 'rope' in line.type['material'] or 'polyester' in line.type['material']:
line.drawLine(time, ax, color=[.3,.5,.5], endpoints=endpoints, shadow=shadow, colortension=colortension, cmap_tension=cmap_tension)
elif 'nylon' in line.type['material']:
line.drawLine(time, ax, color=[.8,.8,.2], endpoints=endpoints, shadow=shadow, colortension=colortension, cmap_tension=cmap_tension)
Expand Down

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